The mass spectral fragmentation patterns of a wide variety of organic molecules are being investigated by several techniques such as isotopic labeling, high resolution mass measurement, metastable ion analyses, etc., in order to develop sufficient insight so that the spectra of unknown compounds can be interpreted effectively or the spectrum of a known substance predicted. This background is required for applying mass spectrometry to many biomedical and organic chemical problems, especially when considering computer-aided methods of spectral interpretation.